FEI Quanta FEG 250, Руководство пользователя

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Operating Procedures: Specimen Preparation and Handling
5-2
Specimen Preparation and Handling
The specimen material for High Vacuum mode must be able to
withstand a low pressure environment (without outgassing) and the
bombardment by electrons. It must be clean and conductive. Oil and
dust may contaminate the chamber environment, which could hinder
or even prevent evacuation to the level needed for standard SEM
operation.
Note:
Always wear lint- / powder-free clean room gloves when reaching into
the specimen chamber to minimise oils, dust, or other contaminants
left inside the chamber.
NEEDED ITEMS
• Class 100 clean-room gloves
• Specimen stubs and conductive adhesive material
• Tools: tweezers, 1.5 mm hex wrench
• Prepared or natural specimen
NATURAL SPECIMEN
If no coating is desired the Low Vacuum mode can be used to
stabilise the specimen for observation. This mode is useful if there is a
suspicion that a coating might alter the specimen.
If the specimen contains any volatile components, such as water or
oil, and therefore will not withstand coating, then the
ESEM mode can
be utilised with the correct environment gas and pressure to allow
observation of the specimen in its natural state.
COATED SPECIMEN
If the specimen is nonconductive (plastic, fibre, polymer or other
substance with an electrical resistance greater than 10
10
ohms) the
specimen can be coated with a thin conductive layer. This conductive
layer reduces beam instability due to sample charging and improves
image quality.
For successful imaging, rough surfaced specimens must be evenly
coated from every direction. Biological, cloth and powder specimens
may require carbon or other conductive painting on portions of the
specimen that are hard to coat.
Coating reduces beam penetration and makes the image sharper. It
may mask elements of interest for X-ray analysis (thus the use of
carbon for geological and biological specimens).
For more information on specific preparation techniques, see
Scanning Electron Microscopy and X-Ray Microanalysis, 2nd ed. by
Joseph Goldstein et al., Plenum Press, New York, 1992.